World War, 1939-1945 471 History 386 Aerial operations 155 Campaigns 142 Naval operations 124 Biography 97 Aerial operations, American 84 Operations research 80 Armed Forces 74 Thesis 73 Aerial operations, British 67 Operating systems (Computers) 67 Naval operations, American 53 Production management 52 World War, 1914-1918 49 Submarine 48 World war, 1939-1945 48 Management 46 Spies 46 Juvenile literature 45 Dissertations, Academic 41 United States 38 Airplanes, Military 36 Commando operations 34 Foreign relations 34 Personal narratives, American 34 Operational readiness 31 Peacekeeping forces 31 Special operations (Military science) 31 World War 31